How to Scab a Cactus

Sharp knives give cactus cuttings clean surfaces that scab well.

The very thing that makes a cactus so successful growing in a hot, dry environment -- storing water in its stem -- also makes it vulnerable when it is wounded. All that moist pulp is open to plant pathogens like bacteria and fungi that could start rot. Hungry and thirsty insects home in on the exposed treat, some of them carrying pathogens into the wound. Once an infection starts, it can spread to the entire plant and kill it. When we wound a cactus by cutting off a piece to propagate it, a scab, or callus, needs to form over the cut end before it is put to root. This hard, corky layer protects the cactus from rotting.

1

Place a clean piece of cardboard in a fully shaded area; it should be longer than the cactus cutting you are going to take. Put on garden gloves. Clean the sharp serrated knife with rubbing alcohol, covering all surfaces well. Grasp the end of the piece of cactus you are going to cut off with kitchen tongs.

2

Make a clean cut through the cactus to give you the length of cutting you want. Avoid jagged or torn edges that won't heal properly or that might harbor pathogens. Lift the cactus cutting away from the parent plant with the tongs once you have cut it off.

3

Put the cutting on the piece of cardboard and leave it there if the cut area is small. Use the tongs to tilt the cutting if it is a large cut and dust the entire cut area with horticultural sulfur or scouring powder. Disinfect a nursery pot a little larger than the stem diameter with 10 percent bleach solution. The pot should have drainage holes. Put the large-diameter cutting into the clean empty pot. Put the cutting upright in its pot in the shade so the stem won't curve while it is scabbing.

4

Leave the cutting in the shade for several days to several weeks or longer, depending on the diameter of the cut, how warm the weather is and how much relative humidity there is. Check the cutting occasionally.

5

Use the tongs to remove the cutting from the cardboard or pot when the cut end is firm and corky, and the tissue is gray or tan with no soft areas. Take the cutting to your potting area.

6

Fill an appropriately sized nursery container that has drainage holes with soilless well-draining potting mix. Bury just enough of the cut stem in the potting mix so the cutting stays erect. Put the container in partial shade until it roots. Don't water it until roots start to form.

Things You Will Need

Sharp serrated knife

Rubbing alcohol

Garden gloves

Kitchen tongs

Clean piece of cardboard

Horticultural sulfur (optional)

Scouring powder (optional)

Nursery pot with drainage holes

Bleach solution, 10 percent

Soilless potting mix

Tips

Take the cutting when the cactus is actively growing. It won't root when it is dormant.

Take care not to wound the cactus while transporting it or potting the cutting, as those wounds will have to scab over as well if they will be below the soil line.

If taking more than one cutting, clean the knife with alcohol between each cut.

When making a large-diameter cut, angle the cut so water will run off the cut surface left behind on the parent plant. If you wish, also dust the cut surface on the parent plant with horticultural sulfur or scouring powder.

Don't use pruning shears to make larger cuts. They crush the tissue so it won't heal properly.

Warning

Pay attention to how you position your hands and fingers while taking the cutting so you avoid long spines that will penetrate the gloves.

About the Author

Cathryn Chaney has worked as a gardening writer since 2002. Her horticultural experience working in the nursery industry informs her garden articles, especially those dealing with arid landscaping and drought-tolerant gardening. Chaney also writes poetry, which has appears in "Woman's World" magazine and elsewhere. Chaney graduated from the University of Arizona in 1992 with a Bachelor of Arts in English.